"If you leave Messi with an open field you know what's going to happen," said an upset Juventus coach.

The rivalry continues as in the new season it was the Argentine magician Lionel Messi who brought FC Barcelona a victory at Camp Nou. The Old Lady side were outclassed by a focused and determined Catalan side since they were knocked out by the Turin side last year in the Champions league quarter finals. A special moment arise when Miralem Pjanic asked Messi for his shirt at halftime, it was clear that Juventus was bowing down to Barcelona and its international cast of stars.

It was only one match, and it was an injury-depleted side visiting Barcelona, but the general sense surrounding Juventus is that last season's finalist has taken a slight step backwards.

The humiliating 3-0 loss on the opening night of the Champions League on Tuesday meant that Juventus has already conceded the same number of goals it allowed in all of last season's competition before it was beaten 4-1 by Real Madrid in the final.

"I think you're exaggerating a bit," Pjanic said in a post-match interview that highlighted the squad's struggles. "You'll see that at the end of the season the results will come."

However, Juventus standout Paulo Dybala was completely outplayed by Messi, his Argentina teammate; center forward Gonzalo Higuain was nearly invisible — just like last season's final — and the Turin squad hardly put up a fight in the second half.

"The absences are not an alibi," Juventus coach Massimiliano Allegri said. "We should have remained in the match in the second half, whereas instead, we made too many errors. If you leave Messi with an open field you know what's going to happen."

Allegri was especially critical of Higuain, another Argentina international who often plays in Messi's shadows.

"He started well but he's got to stay calmer. He lowers his head every time," the coach said.

At the end of a strong first half from Juventus, Messi gave Barcelona the lead following a quick 1-2 with Luis Suarez, rolling a left-foot shot just inside the far post.

"You can't allow a goal like that in the last minute of the first half," said Pjanic, one of Juventus' only decent performers in the match. "It was a serious error. But in general, we've got to be more applied. This will serve as a lesson."

Messi helped make it 2-0 in the 56th minute when Ivan Rakitic scored, and then got another in the 69th that left goalkeeper Gianluigi Buffon, who had not conceded a goal to Messi in their three previous meetings, with no chance.

This is likely Buffon's final season, and the 39-year-old goalkeeper is not having an easy time of it. He was roundly criticized for his performance in Italy's 3-0 loss to Spain in a World Cup qualifier this month.

Juventus also struggled in a 3-2 loss to Lazio in the Italian Super Cup last month and is facing a challenge from Napoli and Inter Milan as it seeks a seventh straight Serie A title.